It is the current practice of financial clearing houses, such as commercial banks, to issue to their customers, periodic statements summarizing transactions for the respective period, and accompanying the statement with the actual transaction documents, e.g., bank checks. This practice has been referred by some as country club billing. A modified version of this practice substitutes facsimile images of the documents for the documents themselves. These images are printed in reduced form or even in abstracted form on the statement itself, with a resultant savings of document handling by both the clearing house and the customer. To produce such a facsimile statement, it is necessary to capture an electronic image of all the checks processed and to manipulate, store and finally print the image. IBM Technical Disclosure Bulletins, Vol. 14, No. 10, March 1972, pages 2944, and Vol. 15, No. 8, January 1973, pages 2443 and 2444 address such a system.
My invention relates to the processing of facsimile image of documents, particularly of financial documents such as bank checks. Bank checks are commonly printed with scenic or patterned backgrounds for both aesthetic and security reasons. In addition, checks are handled by several people and, in the course of their useful life, may be soiled or creased in such a way as to add other non-meaningful marks or pseudo marks such as shadows. All of this background material should be eliminated from the electronic image if a clear, readable output print is to be achieved. Furthermore, any background material that is not eliminated represents useless data that occupies storage and reduces the efficiency of techniques used to compress the image for efficient storage and other computer image manipulation.
Image data is normally separated from background information by a color density threshold value that selects higher density portions as the image data. Known techniques for providing variable analog threshold levels generally represent a compromise between elimination of unwanted background and possible deletion of desired data. It is desirable for an image selection technique to be sensitive to factors other than simply local density to avoid this usual compromise election. Techniques other than simple density thresholding are known. For example, it is known to compute the first and second derivative of the image density to locate the boundaries of an image region. However, these known techniques are not part of a comprehensive system structured to provide a line image selection system capable of distinguishing desirable line images from the type of background image found on modern bank checks.
One object of my invention thus has been to provide an improved image processing system, capable of separating line text from printed background patterns as normally found on bank checks and similar documents.
Typical bank check processing machines operate at high speeds to accommodate the large number of individual documents processed daily. An image processing system, operating in conjunction with the processing of checks, must be capable of matching or exceeding the speed of the check processor; a task which is made difficult by the enormous amount of data represented by the image of even a small bank check. In addition, handling of the resultant image data must be accomplished in synchronism with the check processor and must not consume an impractical amount of computing power or memory space.
Another object of my invention has been to provide an image processor which is capable of operating at speeds compatible with the rate of document presentation normally found in high speed check processors but which requires comparatively low processing and storage capabilities, considering the amount of image data required to be processed.
Image data, as used in facsimile systems, is typically compressed by eliminating redundancy. In a bank check processing machine, it is desirable not only to compress the image data captured, but this compression should be performed as early in the sequence of events as is possible to minimize the total number of computer operations and memory cells required whenever the data is to be handled.
A still further object of my invention has been to provide an image selection process for an image processor that provides output data in a compressed format to reduce the equipment cost and processing steps required for these functions.
Bank checks and similar documents are elongated in the horizontal direction and are processed in equipment that feeds the documents along their long dimension. This arrangement makes it convenient to electronically scan the document by width-wise (vertically) extending scan lines. Printers, on the other hand, such as those that are suitable for printing an image statement, most often print on pages by a scanning print element that moves along a horizontal writing line. Image data captured in vertical scan lines form a document thus must be transformed by 90 degrees to be suitable for use in a horizontal scan printer.
Yet a further object of my invention has been to provide a bank check image processor having an output that is formatted to be readily compatible with the data stream requirements of conventional page printers.
While scanning documents with as image capturing system, it is desirable to know immediately whether the fidelity of the image is acceptable. Immediate knowledge of the image quality permits poor quality documents to be appropriately sorted for special handling while the document is readily accessible. Timely image quality information also makes it possible to halt the useless scanning of documents when the image capture system is malfunctioning.
An additional object of my invention has been to provide reliable means for electronically detecting inferior image data while scanning. The output of such detection is then used to signal the operator, sort the document to a special handling pocket, or indicate the need for maintenance action.